Sunil Amrith - Unruly Waters: How Rains, Rivers, Coasts, and Seas Have Shaped Asia’s History

L OOKING DOWN FROM ORBIT, THE LENS OF A NASA SATELLITE LANDS upon this patch of Earth. In the upper half of the picture lies the curve of a Himalayan mountain range, fringed by the iridescent lakes of the Tibetan plateau.

The satellite picture is a snapshot of a single moment on October 27, 2002. But there are layers of history embedded within it. It shows us the outcome of a process that unfolded in deep time. Approximately 50 million years ago, the Himalayas were created by the collision of what would become the Indian peninsula, which had detached from Madagascar, with the Eurasian landmass. The island buckled under the edge of Eurasia, pushed up the Tibetan Plateau, and eradicated a body of water later named the Tethys Sea. Geology, looking further than religion, E. M. Forster wrote in A Passage to India, knows of a time when neither the river [Ganges] nor the Himalayas that nourish it existed, and an ocean flowed over the holy places of Hindustan.

So massive are the mountains, so heavy is their concentration of snow, ice, heat, and melting water that they shape Earths climate. Asias great rivers are a product of this geological history. They flow south and southeast, and they have shaped the landscape that is visible here: the force of the rivers descending from the mountains eroded rock, creating the gorges and valleys. Over centuries the rivers have carried silt and sediment from the mountains; they have deposited them along Asias valleys and floodplains to sustain large human populations. Writing in the 1950s, guided by maps and not yet by satellite photographs, geographer Norton Ginsburg described Asias mountain core as the hub of a colossal wheel, the spokes of which are formed by some of the greatest rivers in the world.

And then your eye comes to rest on what was invisible to the satellite but is now superimposedevidence of a more recent history lies in the borders that dissect the rivers, their shapes governed by bureaucratic, not environmental, logic. Within the frame of this image alone, the mountains run through southwestern China, Nepal, Bhutan, and northeastern India. The rivers are more unruly; they spill beyond the frame of the photograph. From mountain peaks flow ten great rivers that serve a fifth of humanitythe Tarim, the Amu Darya, the Indus, the Irrawaddy, the Salween, the Mekong, the Yangzi, the Yellow River, and, at the heart of this photograph, the Ganges and the Brahmaputra. The Himalayan rivers run through sixteen countries, nourished by countless tributaries. They traverse the regions we carve up as South, Southeast, East, and Central Asia; they empty out into the Bay of Bengal, the Arabian Sea, the South and East China Seas, and the Aral Sea.

Look at the left of the picture and you can see a more compressed history. The haze of pollution that hangs over North India is a composite brown cloud of human-produced sulfates, nitrates, black carbon, and organic carbon. Aerosol concentrations over the Indian